Gaskets are often used to provide a seal between an engine block and a cylinder head of an internal combustion engine. Cylinder head gaskets typically extend around cylinder bores to provide a combustion seal, maintaining the high temperature gases of combustion within the cylinder bores. The gaskets may also serve to seal fluid flow openings such as coolant and oil openings to prevent undesirable mixing. However, internal combustion engines have recently been operated at increasingly higher engine speeds and with increasingly higher outputs. Therefore, more durable combustion seals are required.
To ensure a satisfactory sealing capacity for both the combustion and fluid seals, it has been known to provide a multi-layer metal gasket with specialized coatings to achieve both a wear resistance seal around the cylinder bores and an effective fluid seal around fluid flow openings. Such gaskets have a high temperature coating with a low coefficient of friction applied around the cylinder bores and an elastomeric coating applied around fluid flow openings. However, gaskets of these types are often expensive and difficult to manufacture, as the coatings are selectively applied to only portions of a side of a particular gasket layer. Therefore it becomes necessary to employ masking techniques, which add production steps and limit the effectiveness of such gaskets.
To overcome the problems associated with masking, one known multi-layer gasket incorporates three plates wherein a particular coating is applied to specific layers of the gasket. A high temperature coating is used to enhance the seal around the combustion bore openings while an elastomeric seal coating is used to enhance the seal surrounding fluid flow openings. While such gaskets operate satisfactory, increased durability around the combustion seal is desired.